Construction of Sydney WestConnex to begin in 2015

The NSW Government is promising WestConnex will clear congestion on Parramatta Road.

AAP: Mick Tsikas

The green light has effectively been given today for Sydney's long-talked about $11.5 billion road network, the WestConnex.

Prime Minister Tony Abbott and New South Wales Premier Barry O'Farrell today released details on the start of the motorway.

The NSW Government is describing the WestConnex as Australia's biggest infrastructure project.

The 33-kilometre WestConnex will link Sydney's west and south-west with the city, airport and Port Botany.

Construction is slated to take eight years and be completed in 2023.

Work will begin in early 2015 with the M4 motorway widened from three lanes to four.

At the same time construction will start on a 5 kilometre tunnel from Homebush Bay Drive to the City West Link.

Work on the M5 East Airport Link will start the year after and an 8.5 kilometre tunnel from Haberfield to St Peters in 2018.

Most of the money for the project will be raised through tolls, with $3.3 billion being committed by the State and Federal Governments.

NSW Roads Minister Duncan Gay says the WestConnex toll will be distance based, similar to the M7.

"If you did the full distance it would be capped somewhere around about $7.60 for 33 kilometres," Mr Gay said.

"We can only firm it up once we've got the full costs in place but on today's costs it would be equal with the cheapest tolls in the city.

"3,000 trucks a day would be removed from Parramatta Road, with an equal improvement in the ambience of those communities and reconnection of those suburbs. If you travelled it you would bypass 52 traffic lights."

But Ken Dopinson, a former director of the Roads and Traffic Authority who is now a member of the transport lobby group 10,000 Friends of Greater Sydney, says he is concerned.

"You've got to always remember these roads, every lane you bring into the city or towards the city will carry 2,000 cars," Mr Dopinson said.

"Not many more people get in those bloody cars. We're talking about a city that's going to expand in the next 40 years by a huge amount. How the hell are you going to carry it?"